Study of the bacterial flagellar motor and its control by chemotactic stimuli will be continued, with the long-term goal of extracting general principles of sensory reception and motor function. The objectives include (a) a quantitative analysis of the use of electrical and chemical components of proton potential to power the motor, (b) elaboration of our finding that protonmotive force regulates as well as energizes the motor, (c) an analysis of the energetics of counterclockwise vs. clockwise rotation, (d) a study of the degree of autonomy of individual flagella on the same cell, using our capacity to record dynamically light microscopic images of single (19 nm diameter) flagella, (e) investigation of the role of mot proteins in motility, and (f) analysis of protein interactions within the motor, by subjecting isolated basal bodies to reversible cross-linking reagents. Species under study are Salmonella, Escherichia coli and Bacillus subtilis.